Cranial studies show that Black skulls became much Whiter-looking after the Civil War. Some of this change was environmental, but most of it was genetic. Not all can be chalked up to ingress with Whites. Apparently Blacks were preferentially selecting Blacks with more progressive features, as these features are more attractive.
White skulls have also gotten much more progressive since the Revolution. In fact, modern White and Black skulls look more like each other than either does to their own ancestors! In other words, modern White skulls look more like modern Blacks than they resemble our own pre-Revolutionary White ancestors! And modern Black skulls look more like modern Whites than they resemble their own pre-Revolutionary Black ancestors.
Both races seem to be converging into a more progressive, less archaic phenotype at the same time as Black and White phenotypes appear to be converging. It is as moderns are merging into sort of a common race in the same way that we are merging into one global culture.
Life is always interesting.